1. Field of the Invention
The present invention relates in general to an apparatus and method of weld joining pipe sections and in particular to groove weld joining of such pipe sections.
2. Description of the Related Art
It is known that in pipe segment welding supports of the molten weld underbead can enhance the pipe surface contour during solidification of the weld. Previous efforts to accomplish this have included solid copper back-up shoes which contact the entire inside surface of the pipe adjacent to the weld zone. These solid copper back-ups must fit tightly and for tubular or circular parts such as pipe sections must be built in sections which expand once inserted into the pipe point workpiece. Other methods which have been used include nonmetallic back-ups such as chemically inactive ceramic or even submerged are welding flux. Nonmetallic backing tend to be expensive or cumbersome to apply.
Prior art pipe section joining apparatus suffered from two major problems in welding pipe sections together. These problems involved installing and removing the underbead support tooling and the creation of weld defects. While copper back-up tooling has been used for years in piping welding it has always been configured as pieces of a pie which expanded out to contact the pipe surface during welding. As such there were always gaps between the segments which caused weld defects as the weld metal was unsupported across these gaps in the tooling. These pie segments then had to be retracted after welding in order to clear the underbead. This required extensive and expensive mechanical systems.
In cases where the copper back ups were not used because of the prohibitive cost of the complicated back-up systems, underbeads of the pipe welds had to be hand ground to a finished form involving great expense. Thus, a new apparatus and method for welding joining pipe sections was needed which would be inexpensive and which could be mounted simply as off a cantilevered boom.